Since an electronic device such as a mobile phone is provided with an interface unit such as an earphone jack and a USB terminal for connection to an external device, and accordingly has an opening from which a connection terminal is exposed is provided in its housing. The provision of the opening means possible infiltration of a material such as liquid and dust via the opening, which is harmful to components inside the housing of the electronic device.
For example, liquid infiltration via the opening might cause some troubles in circuits inside the electronic device.
In response, a conventional art discloses a method of covering such an opening with a rubber cover or the like, so as to prevent liquid and dust from infiltrating via the opening while an earphone or a USB cable is not connected.
Also, another conventional art discloses a method of attaching a waterproof sheet around an earphone jack so as to prevent a material, which has infiltrated via an opening such as liquid and dust, from further infiltrating into other components provided on a substrate. According to this conventional art, attachment of a sheet covering the earphone jack prevents inflow of such a material via the earphone jack.